Headframes for stereotactic neurosurgery are well known. These headframes are ring-shaped structures which are mounted to the skull of a patient to provide a fixed reference with respect to the patient's brain. An arcuate rail has its opposite ends fastened to opposing sides of the headframe and extends above and across the patient's skull. A guide is movably mounted on the rail and can be positioned at any suitable location along the length of the rail to serve as a guide for surgical instruments. Such headframes are commonly used for brain biopsies, tumor removal, or any other modality of deep brain surgery where the surgeon requires guidance to properly position an instrument. In addition, such headframes are useful for cryosurgical treatment of Parkinson's disease, epilepsy, microelectrode guidance, brain nuclei and mapping, placement, positioning, neuronal micro stimulation, recording, lesioning, resection, localization of brain nuclei, micro-injection cannula system, micro injection of drugs, donor human tissue, and the like.
Although a substantial advance over unguided neurosurgery, prior art headframes have significant drawbacks. While the guide can be repositioned to any other location along the plane of the rail, the guide cannot be repositioned transverse to the plane of the rail without removing the headframe from the patient, rotating the headframe so that the plane of the rail passes through the new location, and then remounting the headframe to the patient's skull. Moving the headframe in this manner is too time consuming and too inaccurate.
Thus there is a need for a stereotactic guide apparatus for use with a neurosurgical headframe which permits a tool to be repositioned along any of three axes without having to remove the headframe from the patient.
Another difficulty associated with use of prior art tool guides used with conventional headframes for neurosurgery do not provide adequate control and precision over the positioning of a tool. Since such tool guides are used to position surgical instruments within the brain of a patient, precise control and accuracy are of paramount importance. Thus there is a need for a stereotactic guide apparatus for use with a neurosurgical headframe which provides guidance for a surgical instrument with greater precision and control than heretofore possible.